"The Prime Minister, and others, should consider just what part gardening can play in society. It impacts on those political hot potatoes, law and order, education and health."

While Mr Cameron was educated at Eton and Oxford University, Titchmarsh left school aged 15 with only an O-level in art, before embarking on a career in horticulture.

Writing ahead of National Gardening Week, which starts on April 16, Titchmarsh called for an increase in the number of decently-paid apprenticeships in horticulture. Even those who qualify are unlikely to earn more than £15,000 in the early stage of their career.

"Learning how things grow, from an early age ... gives children a greater understanding of the wider environment, and a greater responsibility for it.

“They will grow up with some affinity with the countryside, rather than living a life glued to mobile phones and computers," he wrote.

While gardening is increasingly popular in Britain, there has been a decline in the number of undergraduates studying botany.

Last month Mr Cameron sought to underline his own green credentials by promising a new generation of “garden cities” across the country as part of the Government’s planning framework.

There is a vegetable patch at Downing Street, although this is maintained by a member of the Prime Minister’s staff.

A Downing Street spokesman said: A Downing Street spokesperson said:"As the Prime Minister has repeatedly made clear on this issue, it is better that people are out working in the community rather than sat at home claiming benefits.

"We recognise that gardening is a rewarding activity be it a hobby or a profession and it brings a great deal of satisfaction to many people."